Searching Optimum Self-Brazing Powder Mixtures Intended for Use in Powder Metallurgy Diamond Tools—A Statistical Approach

At a Glance

Metadata	Details
Publication Date	2025-06-10
Journal	Materials
Authors	A. Romański, Piotr Matusiewicz, Elżbieta Cygan-Bączek
Institutions	Łukasiewicz Research Network - Institute of Non-Ferrous Metals, Jagiellonian University
Analysis	Full AI Review Included

Executive Summary

This study successfully optimized self-brazing powder metallurgy (PM) mixtures for diamond tools, focusing on the relationship between chemical composition and sintered matrix hardness (HV1).

Core Value Proposition: Development of iron-base powder mixtures exhibiting self-brazing capabilities, eliminating the need for secondary brazing operations typically required for cobalt-based matrices in wire saw bead production.
Hardness Control: The resulting matrix hardness was highly tunable, ranging from 260 HV1 to 437 HV1, allowing for precise matching of tool wear resistance to the abrasiveness of the stone workpiece (e.g., high resistance for sandstone, lower resistance for granite).
Compositional Drivers: Statistical analysis (ANOVA) confirmed that Phosphorous (P) content is the dominant factor influencing matrix hardness, with its effect being approximately seven times stronger than that of Nickel (Ni).
Sintering Performance: The materials exhibited excellent sinterability, achieving very low porosity (typically 0.28% to 1.60%), which is critical for superior diamond retention properties.
Predictive Modeling: Two multiple linear regression models were established to predict matrix hardness based on chemical composition, achieving high determination coefficients (R²) of 81.1% (Model 1) and 78.8% (Model 2).

Technical Specifications

Parameter	Value	Unit	Context
Compaction Pressure	260	MPa	Cold compaction, single-action press
Sintering Temperature	950	°C	Isothermal hold temperature
Sintering Time	30	min	Isothermal hold duration
Sintering Atmosphere	Flowing Pure H₂	N/A	Used to prevent oxidation
Heating Rate	15	K/min	Rate during heating phase
Vickers Hardness (HV1) Range	260 to 437	HV1	Measured at 9.81 N (1 kgf) load
Dimensional Change (Shrinkage) Range	-12.81 to -10.81	% (DL/L₀)	Indicates excellent sinterability
Porosity Range (Typical)	0.28 to 1.60	%	Low porosity achieved in most samples (M12 outlier at 7.58%)
Hardness Model (1) R²	81.1	%	Includes Cu, Sn, Ni, P content
Hardness Model (2) R²	78.8	%	Includes Cu, Ni, P content (Sn excluded)
Hardness Dependence	P > Ni > Cu	N/A	P content is the primary driver of hardness

Key Methodologies

The experimental procedure focused on cold compaction followed by controlled sintering, simulating industrial PM processes, and utilizing ANOVA for data analysis.

Raw Material Selection: Commercially available powders were used, including Carbonyl Iron, Carbonyl Nickel, Atomized Copper, Atomized Bronze (10%, 15%, 20% Sn), and Ferrophosphorus (Fe-P, Fe₃P). Mixtures were formulated to ensure sufficient liquid phase content for self-brazing during sintering.
Compaction: Powder mixtures (without lubricant) were cold compacted in a rigid die at 260 MPa to produce 15 x 15 x 5 mm compacts.
Sintering Profile: Specimens were sintered in a laboratory tube furnace at 950 °C for 30 minutes under a flowing pure hydrogen atmosphere. A heating rate of 15 K/min was maintained.
Cooling: Cooling was performed in the furnace and cooling zone to 650 °C to simulate the cooling rate of an industrial belt furnace.
Physical Characterization: Dimensional change (shrinkage) was measured. Density was determined using Archimedes’ principle (ASTM B962-23).
Microstructural Analysis: Porosity was calculated optically (100x magnification) by binarizing micrographs and counting black pixels, ensuring accurate pore mapping without etching.
Mechanical Testing: Hardness was measured using a Vickers indenter (HV1) under a 9.81 N load.
Statistical Modeling: Analysis of Variance (ANOVA) was applied to the data using Statistica software to generate multiple linear regression models linking the chemical composition (Cu, Sn, Ni, P) to the measured HV1 hardness.

Commercial Applications

The developed self-brazing powder mixtures and predictive models are highly relevant for the manufacturing of high-performance abrasive tools.

Wire Saw Bead Production: The primary application is the fabrication of diamond-impregnated beads for wire saws used in quarrying and cutting natural stone (e.g., granite, marble).
Self-Brazing Tool Segments: The mixtures eliminate the costly and time-consuming secondary brazing step required to attach the diamond-impregnated layer to the steel support, streamlining the manufacturing process.
Customizable Wear Resistance: The ability to predict and control matrix hardness (260 HV1 to 437 HV1) via P and Ni content allows manufacturers to tailor tool segments for specific applications:
- High Hardness Matrices: Used for cutting easy-to-cut, highly abrasive materials (e.g., sandstone) where high wear resistance is needed against slurry erosion.
- Lower Hardness Matrices: Used for cutting hard-to-cut materials (e.g., granite) to ensure adequate self-sharpening of the tool.
Advanced PM Matrices: Applicable to other diamond-impregnated tools used in construction, such as segments for circular saws and core drills used for reinforced concrete and ceramics.

View Original Abstract

This paper presents a study on optimising self-brazing powder mixtures for powder metallurgy diamond tools, specifically focusing on wire saws used in cutting natural stone. The research aimed to understand the relationship between the chemical composition of powder mixtures and the hardness of the sintered matrix. The experimental process involved the use of various commercially available powders, including carbonyl iron, carbonyl nickel, atomised bronze, atomised copper, and ferrophosphorus. The samples made of different powder mixtures were compacted and sintered and then characterised by dimensional change, density, porosity, and hardness. The obtained results were statistically analysed using an analysis of variance (ANOVA) tool to create linear regression models that relate the material properties to their chemical composition. The investigated materials exhibited excellent sintering behaviour and very low porosity, which are beneficial for diamond retention. Very good sinterability of powder mixtures can be achieved by tin bronze addition, which provides a sufficient content of the liquid phase and promotes the shrinkage during sintering. Statistical analysis revealed that hardness was primarily affected by phosphorous content, with nickel having a lesser but still significant impact. The statistical model can predict the hardness of the matrix based on its chemical composition. This model, with a determination coefficient of approximately 80%, can be valuable for developing new metal matrices for diamond-impregnated tools, particularly for wire saw beads production.

Tech Support

Original Source

DOI: https://doi.org/10.3390/ma18122726

References

2014 - Comparison of brazed and sintered diamond tools for grinding of stone [Crossref]
2006 - Research and application of cobalt-substitute prealloy powder for diamond tools
2020 - Fabrication and Performance Characterization of Cu-10Sn-xNi Alloy for Diamond Tools
2024 - Effect of sintering process on properties of CuSnZn alloy powder
2009 - Brazing technology of effectively improve diamond tools life and cutting efficiency
2007 - Development of pre-alloyed powders for diamond tools and their characteristics [Crossref]
2021 - Features of the Sintering of Fe-Cu-Sn-Ni and Cu-Ti-Sn-Ni Powders during Hot Pressing [Crossref]